Circuit interrupter contact



48 12, 1952 A. B. RYPlNSKl 2,606,983

CIRCUIT INTERRUPTER CONTACT F iled June 10, 1949 '2O :2 6,. QVENTOZ Patented Aug. 12, 1952 TENT1"-'F IR' uI'r-INTERRUPTE ooNrAc'r Albert B. Rypinski, Laurelton, N. Y assignor a Murray Manufacturing Corporation, Brooklyn, N.,Y., a corporation of New York Application June 10, 1949, serial No. 98,195)

The invention hereindisclosed relates to an electric circuit interrupter and more particularly to an arrangementand construction .of relatively movable contacts in a circuit interrupter.

The primary object of the invention is to provide a construction and arrangement of relatively movable contacts in an electric c'ircuitinterrupter by which wear of the contacts, on repeated interruption of abnormal cu'rrents, is materially and substantially reduced. Another object of the invention is to provide aconstruction and arrangement of such:contacts such that relatively: low melting point metalsisuch as copper and brass may be satisfactorily employedior the contacts instead of the more expensive high melting point metals and alloys such asmolybdenum and tunasten silver. A further object of the invention is to increase the useful life of such contacts.

The foregoing objects and certain advantages that will hereinafter appear are realized in the embodiment of the invention illustrated in the accompanying drawing and described in deta'u below.

The drawing includes: I

Fig. l which is a side elevation of the contact arrangement of a circuit breaker of nominal, rated capacity; such for example as are used in homes and ofiices; I

Fig. 2 which is a transverse, sectional elevation of thecontacts, taken on the line 2- -2 of Fig.1;

Fig. 3 which is a section Similar to Fig-.2, on enlarged'scale, showing the contacts as they separate to interrupt a circuit; and

Fig. 4 which illustrates a modified form of the contacts.

Electric circuit interrupters of the kind herein referred to interrupt the circuit by the separation of relatively movable contacts. Certain such devices, such for example, as automatic circuit breakers, are required to interrupt or break a circuit under overload and short circuit conditions, i. e. interrupt current of ten or more times the normal full load capacity of the contacts. In fact, circuit breakers of fifty ampere capacity are subjected, in tests, to currents of five thousand amperes. On interrupting currents of ten or more times the normal capacity, arcing occurs between the contacts.

When such contacts, as commonly constructed and arranged, break a number of heavy arcs, the parts or sections of the contacts subjected to the arcs wear down due to the burning away of the metal. This burning action is most rapid at the edges of the contacts. This is due to the fact that there is less metal at the edges to absorb and dissipate the heat 2 Claims. (01. 205 -166).

of the are. I Consequently, the edges of the contacts burn off first and the initially fiat contacting surfaces become convexed. Experience has shown that when circuit breakers of a rated capacity of fifty amperes are subjected to currentsof the order of five thousand amperes, the contacts are burned heavily on the first few separations and are rounded off at theedge's.

I have found that by providing a recess in the engaging face of one of the contacts and shaping the other of the contacts complementary to the recess, thawear on the contacts is very materially and substantially reduced. If the contact having the recess thereinbeoi g-reater surface area than the other, so that there is substantial metal about the ,recess a reater contact life is attained, and theefiects of .ar cs formed onthe separation of the contacts ismaterially reduced where'one of the contacts, that having the recess therein, has at least twicethe area and mass as thatwhich is considered normally acceptable.

' Imthearrangement shown inthe drawing, there is a stationary contact t; and a cooperating movablev contact 2.1The stationary contact has a binding post *3 associatedtherewith to which a,

- wire may be connected- The movablecontact 2 upon an overload or short circuitv At the end opposite the contact, the'arm G has a lateral arm I through which there is an elongatedtransverse slot 8. A fixed pin 9 extends through the slot 8, and a spring it between the arm t and a conducting base ll biases the arm about the pivot 5 in a direction to close the contacts. This arrangement is provided to take up contact Wear, and the permissible contact wear will be determined by the length of the slot 8. A flexible connection [2 carries current from the conducting base, which has a terminal l3 thereon, to the arm i and to the movable contact.

In the construction shown, the stationary contact l is at least twice the area and mass of a contact normally used with a circuit breaker of comparable ampere rating, An arcuate recess M is formed in the contacting surface. As will be seen from Figs. 1 and 2, the recess has substantial depth, and there is a substantial amount of metal about the recess. The movable contact has a convexed contacting end portion or surface l5 that is complementary to the recess and that is received in the recess.

With this arrangement and construction of contacts, there are no edges to be readily burned away and there is a comparatively large area of both contacts touching in the closed position of the contacts. This is a very desirable condition and burning of the contacts is reduced to a minimum, there is no concentration of arcing at the contacting surface. Thus, as seen in Fig. 3, where the movable contact 2 is separating from the contact I, an are [6 is carrying current between the contacts. The are is in a narrow, confined space, and in every direction, it is enclosed by relatively large masses of metal tending to cool the are. If the arc succeeds in burning away metal at its points of engagement with the contacts, the distance it must cross is increased and it has a tendency to move to a shorter path. There may, of course, be several arcs simultaneously in the arcing space. The narrow gap and lack of edges tend to equalize the temperatures within the gap.

In Fig. 4 of the drawing, there is illustrated another form for the contacts. With this arrangement, the stationary contact I! is shaped from a flat bar of metal of approximately oneeighth of an inch thick. The recess 18 is produced by raising a circumambient wall I9 all around the area of the recess. Thus, the bottom or back 20 of the contact is in the same plane as the flat bar. From Fig. 4, it will be seen that the recess need not be arcuate; a dish-shaped contact with a complementary surface on the engaging, coopcrating contact 2| provides the characteristics inherent in the invention.

From the foregoing description of the embodiment of the invention illustrated in the drawing, it will be apparent to those skilled in the art that by this invention there is provided an arrangement and construction or contacts in an electric circuit interrupter with which wear of the contacts is materially reduced, with which inexpensive, low melting point metals may be used for the contacts; with which the useful life of the contacts is materially increased; and with which there is materially less emission of flame and molten particles and less mechanical violence and noise on short circuit.

It will be obvious that various changes may be made by those skilled in the art in the details of the embodiment of the invention illustrated in the drawing and described above within the principle and scope of the invention as expressed in the appended claims.

I claim:

1. In a circuit breaker of the kind described, the combination comprising a movable contact arm, a contact fixed to the movable contact arm, a stationary contact positioned to be engaged by said contact fixed to the movable arm in one position of the arm, one of said contacts being fiat and having a recess in the engaging face thereof and the other of said contacts having an engaging surface complementary to and engageable with the surface of said recess, the contact with the recess therein being characterized by the fact that'it has a greater surface area than the other contact, is of greater length and width than the recess therein, and is a least twice the area and the mass normally used in a contact with a circuit breaker of comparable ampere ratin 2. In a circuit breaker of the kind described, the combination comprising a movable contact arm, a' contact having a convexed contacting surface fixed to the movable contact arm, and a flat, stationary contact positioned to be engaged by the contact fixed to the movable contact arm, in one position of the arm, the stationary contact having a recess in the contacting face thereof complementary to the convexed contacting surface of the contact fixed to the movable arm and,

being characterized by the fact that it has a greater length and width than the recess therein, has a greater surface area than the contact fixed to the movable arm, and is at least twice the area and mass normally used with a circuit breaker of comparable ampere rating.

ALBERT B. RYPINSKI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Hiller Jan. 16, 1951 

